Field of the Invention
The present invention relates to circuitry associated with video displays having a picture-in-picture feature.
Television receivers are known in which a second, smaller picture is displayed within the main picture. In the known systems, the baseband video signal for the second picture is digitized and subjected to vertical prefiltering. The vertical prefilter is a low-pass filter whose output is vertically sub-sampled by a 3:1 factor and displayed in a compressed form as part of the main picture. The vertical prefilter is required to band limit the video signal prior to the sub-sampling so as to reduce aliasing artifacts and interline flicker. In the known systems, the analog/digital converter is capable of a five-bit resolution, i.e. has at least five-bits. It provides a five bit video output signal for further processing. The expense involved in a five-bit or over analog/digital converter far exceeds that of a four-bit converter.